Management of a multi-library storage system

ABSTRACT

A computer-implemented method for managing a first storage library and a second storage library, according to one embodiment, includes associating a first physical tape and a second physical tape with a logical tape. The associating includes writing a first identifier to an index of the logical tape. The first identifier represents the first physical tape and the first storage library. The associating further includes writing a second identifier to the index of the logical tape. The second identifier represents the second physical tape and the second storage library. The computer-implemented method further includes storing the index of the logical tape in memory, and displaying the logical tape by reading the index from memory as a file system.

BACKGROUND

The present invention relates to data storage systems, and moreparticularly, this invention relates to management of data within aplurality of storage libraries.

Automated data storage libraries are known for providing cost effectivestorage and retrieval of large quantities of data. The data in automateddata storage libraries is typically stored on media of data storagecartridges that are, in turn, stored at storage slots or the like insidethe library in a fashion that renders the media, and its resident data,accessible for physical retrieval. Such data storage cartridges arecommonly termed “removable media.” Data storage cartridge media maycomprise any type of media on which data may be stored and which mayserve as removable media, including but not limited to magnetic media(such as magnetic tape or disks), optical media (such as optical tape ordiscs), electronic media (such as PROM, EEPROM, flash PROM,CompactFlash™, Smartmedia™, Memory Stick™, etc.), or other suitablemedia. An example of a data storage cartridge that is widely employed inautomated data storage libraries for mass data storage is a magnetictape cartridge.

In addition to data storage media, automated data storage librariestypically comprise data storage drives that store data to, and/orretrieve data from, the data storage cartridge media. Further, automateddata storage libraries typically comprise I/O stations at which datastorage cartridges are supplied or added to, or removed from, thelibrary. The transport of data storage cartridges between data storageslots, data storage drives, and I/O stations is typically accomplishedby one or more accessors. Such accessors have grippers for physicallyretrieving the selected data storage cartridges from the storage slotswithin the automated data storage library and transporting suchcartridges to the data storage drives by moving, for example, in thehorizontal (X) and vertical (Y) directions.

Automated data storage libraries implement magnetic tape for storagerange from small scale to large scale systems. One specific type ofsystem, a linear tape file system (LTFS), is a file system that can beused on tape storage. LTFS offers versions of Library Edition(hereinafter referred to as LE) for a single library, and EnterpriseEdition (hereinafter referred to as EE) which may be applicable tolarger storage systems.

In such systems, tape storage is often suitable for archiving, becausetape storage offers a low capacity unit cost and high recording density.

SUMMARY

A computer-implemented method for managing a first storage library and asecond storage library, according to one embodiment, includesassociating a first physical tape and a second physical tape with alogical tape. The associating includes writing a first identifier to anindex of the logical tape. The first identifier represents the firstphysical tape and the first storage library. The associating furtherincludes writing a second identifier to the index of the logical tape.The second identifier represents the second physical tape and the secondstorage library. The computer-implemented method further includesstoring the index of the logical tape in memory, and displaying thelogical tape by reading the index from memory as a file system.

A computer program product for managing a first storage library and asecond storage library, according to one embodiment, includes a computerreadable storage medium having program instructions embodied therewith.The computer readable storage medium is not a transitory signal per se.The program instructions are readable and/or executable by a controllerto cause the controller to perform the foregoing method.

An apparatus according to one embodiment includes a processor, and logicconfigured to cause the processor of the apparatus to associate, by theprocessor, a first physical tape and a second physical tape with alogical tape. The associating includes writing a first identifier to anindex of the logical tape. The first identifier represents the firstphysical tape and a first storage library. The associating furtherincludes writing a second identifier to the index of the logical tape.The second identifier represents the second physical tape and a secondstorage library. The logic is further configured to cause the processorof the apparatus to store, by the processor, the index of the logicaltape in memory. The logic is further configured to cause the processorof the apparatus to display, by the processor, the logical tape byreading the index from memory as a file system.

Other aspects and embodiments of the present invention will becomeapparent from the following detailed description, which, when taken inconjunction with the drawings, illustrate by way of example theprinciples of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an automated data storage libraryaccording to one embodiment.

FIG. 2 is a perspective view of a storage frame from the data storagelibrary of FIG. 1.

FIG. 3 is a block diagram of an automated data storage library accordingto one embodiment.

FIG. 4 is a block diagram depicting a controller configuration accordingto one embodiment.

FIG. 5A is a front perspective view of a data storage drive according toone embodiment.

FIG. 5B is a rear perspective view of the data storage drive of FIG. 5A.

FIG. 6 is perspective view of a data storage cartridge having a cutawayportion, according to one embodiment.

FIGS. 7A-7B are perspective views of a multi-cartridge deep slot cellaccording to one embodiment.

FIGS. 8A-8D are partial side views of a cartridge blocking mechanismaccording to one embodiment.

FIG. 9 is a depiction of a tiered data storage system in accordance withone embodiment.

FIG. 10A is a flowchart of a method in accordance with one embodiment.

FIG. 10B is a flowchart of sub-operations of an operation of the methodflowchart of FIG. 10A.

FIG. 11 is a portion of an index file in accordance with one embodiment.

FIG. 12 is a portion of an index file in accordance with one embodiment.

FIG. 13 is a diagram of a data storage system in accordance with oneembodiment.

DETAILED DESCRIPTION

The following description is made for the purpose of illustrating thegeneral principles of the present invention and is not meant to limitthe inventive concepts claimed herein. Further, particular featuresdescribed herein can be used in combination with other describedfeatures in each of the various possible combinations and permutations.

Unless otherwise specifically defined herein, all terms are to be giventheir broadest possible interpretation including meanings implied fromthe specification as well as meanings understood by those skilled in theart and/or as defined in dictionaries, treatises, etc.

It must also be noted that, as used in the specification and theappended claims, the singular forms “a,” “an” and “the” include pluralreferents unless otherwise specified.

The following description discloses several preferred embodiments ofstorage systems, as well as operation and/or component parts thereof.

In one general embodiment, a computer-implemented method for managing afirst storage library and a second storage library includes associatinga first physical tape and a second physical tape with a logical tape.The associating includes writing a first identifier to an index of thelogical tape. The first identifier represents the first physical tapeand the first storage library. The associating further includes writinga second identifier to the index of the logical tape. The secondidentifier represents the second physical tape and the second storagelibrary. The computer-implemented method further includes storing theindex of the logical tape in memory, and displaying the logical tape byreading the index from memory as a file system.

In another general embodiment, a computer program product for managing afirst storage library and a second storage library includes a computerreadable storage medium having program instructions embodied therewith.The computer readable storage medium is not a transitory signal per se.The program instructions are readable and/or executable by a controllerto cause the controller to perform the foregoing method.

In another general embodiment, an apparatus includes a processor, andlogic configured to cause the processor of the apparatus to associate,by the processor, a first physical tape and a second physical tape witha logical tape. The associating includes writing a first identifier toan index of the logical tape. The first identifier represents the firstphysical tape and a first storage library. The associating furtherincludes writing a second identifier to the index of the logical tape.The second identifier represents the second physical tape and a secondstorage library. The logic is further configured to cause the processorof the apparatus to store, by the processor, the index of the logicaltape in memory. The logic is further configured to cause the processorof the apparatus to display, by the processor, the logical tape byreading the index from memory as a file system.

FIGS. 1-2 illustrate an automated data storage library 10 which storesand retrieves data storage cartridges, containing data storage media(not shown), from multi-cartridge deep slot cells 100 and singlecartridge storage slots 16. An example of an automated data storagelibrary which has a similar configuration as that depicted in FIGS. 1-2,and may be implemented with some of the various approaches herein is theIBM 3584 UltraScalable Tape Library. Moreover, it should be noted thatreferences to “data storage media” herein refer to data storagecartridges, and for purposes of the present application, the two termsmay be used synonymously.

The library 10 of FIG. 1 comprises a left hand service bay 13, one ormore storage frames 11, and right hand service bay 14. As will bediscussed in further detail below, a frame may comprise an expansioncomponent of the library. Thus, storage frames may be added or removedto expand or reduce the size and/or functionality of the library.According to different approaches, frames may include additional storageslots, deep slot cells, drives, import/export stations, accessors,operator panels, etc.

FIG. 2 shows an exemplary embodiment of a storage frame 11, which actsas the base frame of the library 10. Moreover, the storage frame 11illustrated in FIG. 2 is contemplated to be a minimum configuration ofthe library 10, for which there is only a single accessor 18 (i.e.,there are no redundant accessors) and no service bay. However, in otherembodiments, a storage frame may include multiple robotic accessorsand/or service bays.

Looking to FIG. 2, the library 10 is arranged for accessing data storagemedia in response to commands from at least one external host system(not shown). The library 10 includes a plurality of storage slots 16 onfront wall 17 and a plurality of multi-cartridge deep slot cells 100 onrear wall 19, both of which may be used for storing data storagecartridges that may contain data storage media. According to oneapproach, the storage slots 16 are configured to store a single datastorage cartridge, and the multi-cartridge deep slot cells 100 areconfigured to store a plurality of data storage cartridges. In apreferred approach, the multi-cartridge deep slot cells may be arrangedin sequential order of tiers from front to rear (e.g., see FIG. 7A).

With continued reference to FIG. 2, the storage frame 11 of the library10 also includes at least one data storage drive 15, e.g., for readingand/or writing data with respect to the data storage media.Additionally, a first accessor 18 may be used to transport data storagemedia between the plurality of storage slots 16, the multi-cartridgedeep slot cells, and/or the data storage drive(s) 15. According tovarious approaches, the data storage drives 15 may be optical discdrives, magnetic tape drives, solid state drives having nonvolatilerandom access memory (NVRAM) such as Flash memory, or other types ofdata storage drives as are used to read and/or write data with respectto the data storage media.

As illustrated, the storage frame 11 may optionally include an operatorpanel or other user interface, such as a web-based interface, whichallows a user to interact with the library 10. The storage frame 11 mayalso optionally comprise an upper I/O station 24 and/or a lower I/Ostation 25, thereby allowing data storage cartridges to be added (e.g.,inserted) to the library inventory and/or removed from the librarywithout disrupting library operation. Furthermore, the library 10 mayhave one or more storage frames 11, each having storage slots 16,preferably accessible by the first accessor 18.

As described above, the storage frames 11 may be configured withdifferent components depending upon the intended function. Oneconfiguration of storage frame 11 may comprise storage slots 16 and/ormulti-cartridge deep slot cells 100, data storage drive(s) 15, and otheroptional components to store and retrieve data from the data storagecartridges. However, in another approach, a storage frame 11 may includestorage slots 16 and/or multi-cartridge deep slot cells 100 and no othercomponents. The first accessor 18 may have a gripper assembly 20, e.g.,for gripping one or more data storage media, in addition to having a barcode scanner or other reading system, such as a cartridge memory readeror similar system mounted on the gripper assembly 20, to “read”identifying information about the data storage media.

FIG. 3 depicts an automated data storage library 10, in accordance withone embodiment. As an option, the present automated data storage library10 may be implemented in conjunction with features from any otherembodiment listed herein, such as those described with reference to theother FIGS. Of course, however, such automated data storage library 10and others presented herein may be used in various applications and/orin permutations which may or may not be specifically described in theillustrative embodiments listed herein. Further, the automated datastorage library 10 presented herein may be used in any desiredenvironment. Thus FIG. 3 (and the other FIGS.) should be deemed toinclude any and all possible permutations.

Referring now to FIG. 3, the automated data storage library 10 asdescribed in reference to FIGS. 1 and 2, is depicted according to oneembodiment. According to a preferred approach, the library 10 may employa controller, e.g., arranged as a distributed system of modules with aplurality of processor nodes.

In one approach, the library is controlled, not by a central controller,but rather, by a distributed control system for receiving logicalcommands and converting the commands to physical movements of theaccessor and gripper, and for operating the drives in accordance withthe desired physical movements. The distributed control system may alsoprovide logistical support, such as responding to host requests forelement status, inventory, library status, etc. The specific commands,the conversion of those commands to physical movements, and theoperation of the drives may be of a type known to those of skill in theart.

While the automated data storage library 10 has been described asemploying a distributed control system, various other approachesdescribed and/or suggested herein may be implemented in automated datastorage libraries regardless of control configuration, such as, but notlimited to, an automated data storage library having one or more librarycontrollers that are not distributed.

Referring still to FIG. 3, the library 10 may have one or more storageframes 11, a left hand service bay 13 and a right hand service bay 14.The left hand service bay 13 is shown with a first accessor 18, where,as discussed above, the first accessor 18 may include a gripper assembly20 and/or a bar code scanner (e.g., reading system) to “read”identifying information about the data storage media depending on thedesired embodiment. Furthermore, the right hand service bay 14 is shownhaving a second accessor 28, which includes a gripper assembly 30 andmay also include a reading system 32 to “read” identifying informationabout the data storage media.

According to one approach, in the event of a failure or otherunavailability of the first accessor 18, or its gripper assembly 20,etc., the second accessor 28 may perform some or all of the functions ofthe first accessor 18. Thus, in different approaches, the two accessors18, 28 may share one or more mechanical paths, they may have completelyindependent mechanical paths, or combinations thereof. In one example,the accessors 18, 28 may have a common horizontal rail with independentvertical rails to travel therealong. Moreover, it should be noted thatthe first and second accessors 18, 28 are described as first and secondfor descriptive purposes only and this description is not meant to limiteither accessor to an association with either the left hand service bay13, or the right hand service bay 14.

In an exemplary embodiment which is in no way intended to limit theinvention, the first and second accessors 18, 28 may preferably movetheir grippers in at least two directions, called the horizontal “X”direction and vertical “Y” direction, e.g., to retrieve and grip,deliver and release, load and unload, etc. the data storage cartridge atthe storage slots 16, multi-cartridge deep slot cells 100, data storagedrives 15, etc.

With continued reference to FIG. 3, library 10 receives commands fromone or more host systems 40, 41, 42. The host systems 40, 41, 42, suchas host servers, communicate with the library directly, e.g., on path80, through one or more control ports (not shown), or through one ormore data storage drives 15 on paths 81, 82. Thus, in differentapproaches, the host systems 40, 41, 42 may provide commands to accessparticular data storage cartridges and move the cartridges, for example,between the storage slots 16 and the data storage drives 15. Thecommands are typically logical commands identifying the cartridges orcartridge media, and/or logical locations for accessing the media.Furthermore, it should be noted that the terms “commands” and “workrequests” are used interchangeably herein to refer to suchcommunications from the host system 40, 41, 42 to the library 10 as areintended to result in accessing particular data storage media within thelibrary 10 depending on the desired approach.

According to one embodiment, the library 10 may be controlled by alibrary controller. Moreover, in various approaches, the librarycontroller may include a distributed control system receiving thelogical commands from hosts, determining the required actions, and/orconverting the actions to physical movements of the first and/or secondaccessor 18, 28. In another approach, the distributed control system mayhave a plurality of processor nodes, each having one or more computerprocessors. According to one example of a distributed control system, acommunication processor node 50 may be located in a storage frame 11.The communication processor node provides a communication link forreceiving the host commands, either directly or through the drives 15,via at least one external interface, e.g., coupled to line 80.

Still referring to FIG. 3, the communication processor node 50 mayadditionally provide a communication link 70 for communicating with thedata storage drives 15. As illustrated, the communication processor node50 may preferably be located in the storage frame 11, e.g., close to thedata storage drives 15. Furthermore, one or more additional workprocessor nodes may be provided to form an exemplary distributedprocessor system, which may comprise, e.g., a work processor node 52located at first accessor 18, and that is coupled to the communicationprocessor node 50 via a network 60, 157. According to differentapproaches, each work processor node may respond to received commandsthat are broadcast thereto from any communication processor node, andthe work processor nodes may also direct the operation of the accessors,e.g., providing move commands. An XY processor node 55 may be providedand may be located at an XY system of first accessor 18. As illustrated,the XY processor node 55 is coupled to the network 60, 157, and isresponsive to the move commands, operating the XY system to position thegripper assembly 20.

Also, an operator panel processor node 59 may be provided at theoptional operator panel for providing an interface for communicatingbetween the operator panel and the communication processor node 50, thework processor nodes 52, 252, and the XY processor nodes 55, 255.

A network 60, for example comprising a common bus, is provided, couplingthe various processor nodes. The network may comprise a robust wiringnetwork, such as the commercially available Controller Area Network(CAN) bus system, which is a multi-drop network, having a standardaccess protocol and wiring standards, for example, as defined by CiA,the CAN in Automation Association, Am Weich Selgarten 26, D-91058Erlangen, Germany. Other networks, such as Ethernet, or a wirelessnetwork system, such as RF or infrared, may be employed in the libraryas is known to those of skill in the art. In addition, multipleindependent networks may also be used to couple the various processornodes.

As illustrated in FIG. 3, the communication processor node 50 is coupledto each of the data storage drives 15 of a storage frame 11, via lines70, and are thereby communicating with the drives 15 and with hostsystems 40, 41, 42. Alternatively, the host systems 40, 41, 42 may bedirectly coupled to the communication processor node 50, at input 80 forexample, or to control port devices (not shown) which connect thelibrary to the host system(s) with a library interface similar to thedrive/library interface. As is known to those of skill in the art,various communication arrangements may be employed for communicationwith the hosts and with the data storage drives. In the example of FIG.3, host connections 80 and 81 are intended to be Ethernet and a SCSIbus, respectively, e.g., and may serve as host connections. However, bus82 comprises an example of a Fibre Channel bus which is a high speedserial data interface, allowing transmission over greater distances thanthe SCSI bus systems.

According to some approaches, the data storage drives 15 may be in closeproximity to the communication processor node 50, and may employ a shortdistance communication scheme, such as Ethernet, or a serial connection,such as RS-422. Thus, the data storage drives 15 may be individuallycoupled to the communication processor node 50 by lines 70.Alternatively, the data storage drives 15 may be coupled to thecommunication processor node 50 through one or more networks.

Furthermore, additional storage frames 11 may be provided, whereby eachis preferably coupled to the adjacent storage frame. According tovarious approaches, any of the additional storage frames 11 may includecommunication processor nodes 50, storage slots 16, data storage drives15, networks 60, etc.

Moreover, as described above, the automated data storage library 10 maycomprise a plurality of accessors. A second accessor 28, for example, isshown in a right hand service bay 14 of FIG. 3. The second accessor 28may include a gripper assembly 30 for accessing the data storage media,and an XY system 255 for moving the second accessor 28. The secondaccessor 28 may run on the same horizontal mechanical path as the firstaccessor 18, and/or on an adjacent (e.g., separate) path. Moreover, theillustrative control system additionally includes an extension network200 which forms a network coupled to network 60 of the storage frame(s)11 and to network 157 of left hand service bay 13.

In FIG. 3 and the accompanying description, the first and secondaccessors are associated with the left hand service bay 13 and the righthand service bay 14 respectively. However, this is for illustrativepurposes and there may not be an actual association. Thus, according toanother approach, network 157 may not be associated with the left handservice bay 13 and network 200 may not be associated with the right handservice bay 14. Moreover, depending on the design of the library, it maynot be necessary to have a left hand service bay 13 and/or a right handservice bay 14 at all.

An automated data storage library 10 typically comprises one or morecontrollers to direct the operation of the automated data storagelibrary. Moreover, host computers and data storage drives typicallyinclude similar controllers. A library controller may take manydifferent forms and may comprise, for example, but is not limited to, anembedded system, a distributed control system, a personal computer, aworkstation, etc. The term “library controller” as used herein isintended in its broadest sense as a device that includes at least oneprocessor, and optionally further circuitry and/or logic, forcontrolling and/or providing at least some aspects of libraryoperations.

Referring now to FIG. 4, a typical controller 400 is shown with aprocessor 402, Random Access Memory (RAM) 403, nonvolatile memory 404,device specific circuits 401, and I/O interface 405. Alternatively, theRAM 403 and/or nonvolatile memory 404 may be contained in the processor402 as could the device specific circuits 401 and I/O interface 405. Theprocessor 402 may comprise, for example, an off-the-shelfmicroprocessor, custom processor, Field Programmable Gate Array (FPGA),Application Specific Integrated Circuit (ASIC), discrete logic, etc. TheRAM 403 is typically used to hold variable data, stack data, executableinstructions, etc.

According to various approaches, the nonvolatile memory 404 may compriseany type of nonvolatile memory such as, but not limited to, ElectricallyErasable Programmable Read Only Memory (EEPROM), flash Programmable ReadOnly Memory (PROM), battery backup RAM, hard disk drives, etc. However,the nonvolatile memory 404 is typically used to hold the executablefirmware and any nonvolatile data. Moreover, the I/O interface 405comprises a communication interface that allows the processor 402 tocommunicate with devices external to the controller. Examples maycomprise, but are not limited to, serial interfaces such as RS-232, USB(Universal Serial Bus) or Small Computer Systems Interface (SCSI). Thedevice specific circuits 401 provide additional hardware to enable thecontroller 400 to perform unique functions including, but not limitedto, motor control of a cartridge gripper. Moreover, the device specificcircuits 401 may include electronics that provide, by way of example butnot limitation, Pulse Width Modulation (PWM) control, Analog to DigitalConversion (ADC), Digital to Analog Conversion (DAC), etc. In addition,all or part of the device specific circuits 401 may reside outside thecontroller 400.

While the automated data storage library 10 is described as employing adistributed control system, the various approaches described and/orsuggested herein may be implemented in various automated data storagelibraries regardless of control configuration, including, but notlimited to, an automated data storage library having one or more librarycontrollers that are not distributed. Moreover, a library controller maycomprise one or more dedicated controllers of a library, depending onthe desired embodiment. For example, there may be a primary controllerand a backup controller. In addition, a library controller may compriseone or more processor nodes of a distributed control system. Accordingto one example, communication processor node 50 (e.g., of FIG. 3) maycomprise the library controller while the other processor nodes (ifpresent) may assist the library controller and/or may provide backup orredundant functionality. In another example, communication processornode 50 and work processor node 52 may work cooperatively to form thelibrary controller while the other processor nodes (if present) mayassist the library controller and/or may provide backup or redundantfunctionality. Still further, all of the processor nodes may comprisethe library controller. According to various approaches described and/orsuggested herein, a library controller may have a single processor orcontroller, or it may include multiple processors or controllers.

FIGS. 5A-5B illustrate the front 501 and rear 502 views of a datastorage drive 15, according to one embodiment. In the example depictedin FIGS. 5A-5B, the data storage drive 15 comprises a hot-swap drivecanister, which is in no way intended to limit the invention. In fact,any configuration of data storage drive may be used whether or not itincludes a hot-swap canister. As discussed above, a data storage drive15 is used to read and/or write data with respect to the data storagemedia, and may additionally communicate with a memory which is separatefrom the media, and is located within the cartridge. Thus, according toone approach, a data storage cartridge may be placed into the datastorage drive 15 at opening 503.

Furthermore, FIG. 6 illustrates an embodiment of a data storagecartridge 600 with a cartridge memory 610 shown in a cutaway portion ofthe Figure, which is in no way intended to limit the invention. In fact,any configuration of data storage cartridge may be used whether or notit comprises a cartridge memory. According to various approaches, mediaof the data storage cartridge media may include any type of media onwhich data may be stored, including but not limited to magnetic media,e.g., magnetic tape, disks, etc.; optical media, e.g., optical tape,discs, etc.; electronic media, e.g., PROM, EEPROM, flash PROM,CompactFlash™, Smartmedia™, Memory Stick™, etc.; etc., or other suitablemedia. Moreover, an example of a data storage cartridge that is widelyemployed in automated data storage libraries for mass data storage is amagnetic tape cartridge in which the media is magnetic tape.

Looking now to FIGS. 7A-7B, a multi-cartridge deep slot cell 100 havingbiasing springs 152 is depicted according to one embodiment. As shown inthe illustrative embodiment, the multi-cartridge deep slot cell 100comprises a housing 110 defining an interior space 115. Furthermore, aplurality of storage slots 120 is disposed within the housing, and maybe configured for storing up to a plurality of data storage cartridges600, depending on the desired approach. Alternatively, themulti-cartridge deep slot cell 100 may be built into the frame of theautomated data storage library according to one approach.

FIGS. 8A-8D illustrate an embodiment of a cartridge blocking mechanism150 having a retaining gate 660 that retains the data storage cartridgesin the multi-cartridge deep slot cell 100 according to one embodiment.As illustrated, according to one approach, the retaining gate 660 may beexternally attached to a multi-cartridge deep slot cell 100, relative toa front opening of the multi-cartridge deep slot cell 100, whereby theretaining gate 660 can be activated by an accessor 18, e.g., of anautomated tape library. Moreover, the retaining gate 660 allows forpositive cartridge retention against the pressure of biasing springs(see 152 of FIGS. 7A-7B), and ensures that one or more data storagecartridges do not get pushed out of the multi-cartridge deep slot cell100 simultaneously, while allowing the pushing mechanism (not shown) ofthe multi-cartridge deep slot cell 100 to continuously push data storagecartridge(s) to the opening in a multi-cartridge deep slot cell 100.Thus, according to one approach, the accessor 18 may open the retaininggate to gain access to the data storage cartridge in tier 1 and, uponits extraction, the biasing spring 152 moves the cartridge(s) positionedbehind the extracted cartridge forward, thereby promoting thecartridge(s) by one tier as will soon become apparent.

The basic working of the retaining gate is that the gate prevents thedata storage cartridge(s) from being pushed out of a multi-cartridgedeep slot cell 100. For example, as shown in FIGS. 8A-8D, a retaininggate 660 can be lifted by, for example, accessor 18 or by a frontstorage cartridge 642 for cartridge removal from/insertion into amulti-cartridge deep slot cell 100. Specifically, retaining gate 660 hasa pivoting arm 661 mounted on multi-cartridge deep slot cell 100 via apivoting post (not shown) that can be integral to a construction ofmulti-cartridge deep slot cell 100. Pivoting arm 661 is located below acatch 662 of retaining gate 660 whereby a thrust force TF through datastorage cartridge 644-642 caused by the pushing mechanism (not shown) ofmulti-cartridge deep slot cell 100 causes retaining gate 660 to stayclosed in a retaining position as shown in FIG. 8A. Moreover, theretaining gate 660 is preferably biased such that it closes in thedownward direction over the front opening of multi-cartridge deep slotcell 100. This constant biasing may be achieved via gravity as shown inFIG. 8A or by implementing a spring force, e.g., attached to retaininggate 660 (not shown).

For removal of front storage cartridge 642 by accessor 18 frommulti-cartridge deep slot cell 100, retaining gate 660 must be liftedupward to a releasing position whereby catch 662 of retaining gate 660is disengaged from front storage cartridge 642. This can be seen in FIG.8B where accessor 18 interfaces with retaining gate 660 by providing alifting force. Once retaining gate 660 is lifted to the releasingposition and accessor 18 is engaged with storage cartridge 642, accessor18 can pull storage cartridge 642 out of multi-cartridge deep slot cell100 and into accessor 18 without any interference of retaining gate 660as shown in FIG. 8C. In view of storage cartridges 644 and 643 beingstored in multi-cartridge deep slot cell 100, retaining gate 660 mustreturn to its retaining position to prevent storage cartridges 644 and643 from being ejected from multi-cartridge deep slot cell 100 by thethrust force TF of the pushing mechanism (not shown). During extractionof front storage cartridge 642 through the front opening ofmulti-cartridge deep slot cell 100, the retaining gate 660, which isbeing biased downward, moves back to the retaining position to engagestorage cartridge 643.

Once front storage cartridge 642 is extracted and storage cartridges 643and 644 are retained from being pushed out of multi-cartridge deep slotcell 100, retaining gate 660 has successfully completed its cartridgeretrieval process. Now retaining gate 660 demonstrates its ability towork for cartridge insertion into multi-cartridge deep slot cell 100.When accessor 18 begins to insert storage cartridge 642 back intomulti-cartridge deep slot cell 100, retaining gate 660 is lifted to itsreleasing position to allow storage cartridge 642 through the frontopening of multi-cartridge deep slot cell 100. Catch 662 of retaininggate 660 interfaces with a rear portion of storage cartridge 642, inparticular a beveled surface of catch 662 as shown in FIG. 8D, wherebyretaining gate 660 is lifted to its releasing position as shown in FIG.8B due to storage cartridge 642 being pushed in multi-cartridge deepslot cell 100 by accessor 18. In doing so, storage cartridges 644, 643are pushed deeper into multi-cartridge deep slot cell 100 by storagecartridge 642 in multi-cartridge deep slot cell 100 by accessor 18.Thus, the accessor is able to provide a force greater than the thrustforce TF antiparallel thereto, to overcome the directional biasing ofthe storage cartridges 644, 643. Upon full insertion intomulti-cartridge deep slot cell 100, retaining gate 660 moves to itsretaining position to engage storage cartridge 642 as shown in FIG. 8A.

Thus, looking to various embodiments presented herein, access to astorage slot may include the ability to remove a cartridge from astorage slot, the ability to place a cartridge into a storage slot, orcombinations thereof.

According to an exemplary embodiment, the storage slots from top tobottom are considered to be in parallel and comprise the same tier.Moreover, the storage slots from front to back, in a particular row, areconsidered to be in series and comprise sequential tiers.

Referring back to FIGS. 7A-7B, in accordance with one embodiment,storage slots 120 are depicted as being configured for storing up to aplurality of data storage cartridges 600, and arranged in sequentialorder of tiers 621, 622, 623, 624, 625 from front to rear. It should benoted that the frontmost tier 621 is also called “tier 1”, while thenext tier 622 is called “tier 2”, etc., and the last tier 625 is alsocalled the “rearmost” tier. However, referring to FIG. 2, in oneembodiment, the single cartridge storage slots 16 are also termed “tier0”.

Referring again to FIGS. 1-3, according to one embodiment, thecontroller of automated data storage library 10 may operate theaccessor(s) 18, 28 to selectively extract, place and/or transport datastorage cartridges with respect to the multi-cartridge deep slot cells100 and/or other elements of the automated data storage library 10. Forexample, the controller may facilitate extracting a cartridge from amulti-cartridge deep slot cell 100, transporting the cartridge to a datastorage drive 15 and placing the cartridge in the drive 15. Thecontroller may then extract the cartridge from the data storage drive15, while directing the accessor to transport the cartridge to aspecific multi-cartridge deep slot cell 100, and place the cartridgetherein.

In one embodiment, one or more data storage cartridges may be added intothe library, e.g., at an I/O station 24, 25, whereby the controller ofthe automated data storage library 10 may then operate the accessor(s)18, 28 to transport the cartridge(s) to specific multi-cartridge deepslot cell(s) 100, and place the cartridge(s) therein. Similarly, thecontroller may operate the accessor(s) to selectively extract, place andtransport data storage cartridges with respect to the single cartridgestorage slots 16, and/or transport inserted or added cartridge(s) tospecific single cartridge storage slots 16.

Now referring to FIG. 9, a storage system 900 is shown according to oneembodiment. Note that some of the elements shown in FIG. 9 may beimplemented as hardware and/or software, according to variousembodiments. In some approaches, the storage system 900 may beimplemented in an automated data storage library such as that shown inFIGS. 1-2. In other approaches, an automated data storage library suchas that shown in FIGS. 1-2 may be a tier of the storage system 900.

The storage system 900 may include a storage system manager 912 forcommunicating with a plurality of media on at least one higher storagetier 902 and at least one lower storage tier 906. The higher storagetier(s) 902 preferably may include one or more random access and/ordirect access media 904, such as hard disks in hard disk drives (HDDs),nonvolatile memory (NVM), solid state memory in solid state drives(SSDs), flash memory, SSD arrays, flash memory arrays, etc., and/orothers noted herein or known in the art. The lower storage tier(s) 906may preferably include one or more lower performing storage media 908,including sequential access media such as magnetic tape in tape drivesand/or optical media, slower accessing HDDs, slower accessing SSDs,etc., and/or others noted herein or known in the art. One or moreadditional storage tiers 916 may include any combination of storagememory media as desired by a designer of the system 900. Also, any ofthe higher storage tiers 902 and/or the lower storage tiers 906 mayinclude some combination of storage devices and/or storage media.

The storage system manager 912 may communicate with the storage media904, 908 on the higher storage tier(s) 902 and lower storage tier(s) 906through a network 910, such as a storage area network (SAN), as shown inFIG. 9, or some other suitable network type. The storage system manager912 may also communicate with one or more host systems (not shown)through a host interface 914, which may or may not be a part of thestorage system manager 912. The storage system manager 912 and/or anyother component of the storage system 900 may be implemented in hardwareand/or software, and may make use of a processor (not shown) forexecuting commands of a type known in the art, such as a centralprocessing unit (CPU), a field programmable gate array (FPGA), anapplication specific integrated circuit (ASIC), etc. Of course, anyarrangement of a storage system may be used, as will be apparent tothose of skill in the art upon reading the present description.

In more embodiments, the storage system 900 may include any number ofdata storage tiers, and may include the same or different storage memorymedia within each storage tier. For example, each data storage tier mayinclude the same type of storage memory media, such as HDDs, SSDs,sequential access media (tape in tape drives, optical disc in opticaldisc drives, etc.), direct access media (CD-ROM, DVD-ROM, etc.), or anycombination of media storage types. In one such configuration, a higherstorage tier 902, may include a majority of SSD storage media forstoring data in a higher performing storage environment, and remainingstorage tiers, including lower storage tier 906 and additional storagetiers 916 may include any combination of SSDs, HDDs, tape drives, etc.,for storing data in a lower performing storage environment. In this way,more frequently accessed data, data having a higher priority, dataneeding to be accessed more quickly, etc., may be stored to the higherstorage tier 902, while data not having one of these attributes may bestored to the additional storage tiers 916, including lower storage tier906. Of course, one of skill in the art, upon reading the presentdescriptions, may devise many other combinations of storage media typesto implement into different storage schemes, according to theembodiments presented herein.

According to some embodiments, the storage system (such as 900) mayinclude logic configured to receive a request to open a data set, logicconfigured to determine if the requested data set is stored to a lowerstorage tier 906 of a tiered data storage system 900 in multipleassociated portions, logic configured to move each associated portion ofthe requested data set to a higher storage tier 902 of the tiered datastorage system 900, and logic configured to assemble the requested dataset on the higher storage tier 902 of the tiered data storage system 900from the associated portions. Of course, this logic may be implementedas a method on any device and/or system or as a computer programproduct, according to various embodiments.

Despite tape storage providing a low capacity unit cost and highrecording density storage option, some users opt for cloud storage forarchiving data rather than local tape-based storage systems. One of thereasons for this is perhaps because cloud storage enables starting-up socalled “small start.”

Large scale tape storage sometimes has an associated large start-upcost. In view of this, a “scale-up” approach is sometimes implemented.In a scale up approach, a system begins with a small library, andsubsequently replaces the small library with a larger library when thelibrary's collective amount of data approaches a storage capacity of thelibrary.

Another approach is sometimes referred to as a “scale-out” approach, inwhich the size of an initial library is increased in a step-by-stepmanner as data requirements of the library increase. Furtherdescriptions of this scale-out approach will now be provided below inthe context of using LE or EE.

In LE, each of the tape cartridges in a library are presented as asubdirectory under the mount point of an LTFS, in the perspective of thefile system. Thus, a user can positively instruct which cartridge is tobe used for writing and/or reading a file, or confirm which cartridgehas previously been used for writing or reading a file. LE offers anadvantage of enabling a user to specify a tape as the path name of afile (of data) when selecting the tape from an external applicationusing LE. However, LE systems are executed on a single server for asingle library connected to the server, and LE systems are notapplicable for the scale-out approach.

It is possible to use a plurality of libraries on a plurality of LEsystems at the same time. However, in this case, for each of thelibraries, an LE system is activated on a server to which the library isconnected, and the library is connected to a mount point on the sameserver. As a result, to specify a file, the server name and the pathname may need to be specified.

In addition, because a single LE system is installed for each of theplurality of paralleled libraries, when access concentration occurs on atape managed under an LE system, a drive of the corresponding librarymay only be used. This is even despite other drives of other librariespotentially not being in use. Accordingly, some advantages of thescale-out approach and/or components associated therewith may remain notfully utilized.

It should be noted that here, it is assumed that a set of a library anda server executing an LE system are to be added when scaling-out thesystem. Executing two or more LE systems on the same server is possible,but it is not preferred in the perspective of scale-out because of theload incurred on the server. In addition, because LE systems may callfor different respective mount points when a plurality of LE systems areexecuted on the same server, a path name may need to be modifiedaccording to the library in which the corresponding tape exists. Thus,it is still not feasible and/or possible to continue to use the samepath name as was used before scaling-out the system.

To further elaborate the effects of scaling-out a system, a scheme ofdefining logical tape cartridges and assigning a plurality of physicaltape cartridges to one logical tape cartridge will now be considered.This scheme may hereafter be referred to as a Multi-Tape File System(MTFS).

An MTFS may operate as an upper layer of a plurality of LE systems, andprovide users with a file system that presents logical tape cartridgesas folders. A commonly considered method of MTFS includes storing atable containing information of logical tapes, physical tapes, and thelibraries (servers) that manage the physical tapes in the MTFS, and,upon receiving a request, e.g., from a user, retrieving the names of theserver and the physical tape cartridge corresponding to the request.

Referring now to EE applications, EE is typically used in largersystems, and supports configurations of multiple libraries. However, anEE system is a hierarchical storage management (HSM) system which workswith a distributed file system. Although it is capable of writing datato and reading data from a tape library system, it operates under themanagement of the HSM system. Accordingly, EE systems generally do notallow a user to explicitly specify a physical tape for writing data to.In addition, the reading of a data file is also performed generallythrough a distributed file system by the nature of the HSM. Accordingly,for use cases in which use of an HSM system is appropriate, EE may be anoption. However, for the above-described use case, in which an externalapplication controls relationships between files and recording tapes, EEmay not be an appropriate choice for use.

In an EE system, the destination for storing a data is often specifiedas a “tape pool” (corresponding to a set of physical tapes), rather thanas single physical tape. Accordingly, when recording a plurality offiles of data on a tape pool, the files can be recorded on separatephysical tapes belonging to the same tape pool. This feature of EEenables similar advantages of scaling-out by using a plurality of drives(as previously discussed in the descriptions of MTFS). However, accessesto a plurality of files stored on the same physical tape leads to use ofonly single drive, which is not efficient. In addition, a tape poolcannot be specified across a plurality of libraries, and thus advantagesof scale-out, by increasing libraries, cannot be obtained by a singletape pool.

Various embodiments described herein may be utilized for enablingscale-out configuration of a storage system, while maintaining one ormore features of subfolders. In particular, such embodiments establish alogical tape to which physical tapes of different storage libraries areassociated.

Now referring to FIG. 10A, a flowchart of a method 1000 is shownaccording to one embodiment. The method 1000 may be performed inaccordance with the present invention in any of the environmentsdepicted in FIGS. 1-9, among others, in various embodiments. Of course,more or less operations than those specifically described in FIG. 10Amay be included in method 1000, as would be understood by one of skillin the art upon reading the present descriptions.

Each of the steps of the method 1000 may be performed by any suitablecomponent of the operating environment. For example, in variousembodiments, the method 1000 may be partially or entirely performed by acomputer, or some other device having one or more processors therein.The processor, e.g., processing circuit(s), chip(s), and/or module(s)implemented in hardware and/or software, and preferably having at leastone hardware component may be utilized in any device to perform one ormore steps of the method 1000. Illustrative processors include, but arenot limited to, a central processing unit (CPU), an application specificintegrated circuit (ASIC), a field programmable gate array (FPGA), etc.,combinations thereof, or any other suitable computing device known inthe art.

It should be prefaced that method 1000 may be utilized for managing afirst tape storage library and a second tape storage library.

Method 1000 includes associating a first physical tape and a secondphysical tape with a logical tape, e.g., see operation 1002. Accordingto various approaches, the first physical tape and/or the secondphysical tape may include any type of physical tape. In a preferredapproach, the first physical tape and the second physical tape aremagnetic recording tapes.

Looking to FIG. 10B, exemplary sub-operations of associating the firstphysical tape and the second physical tape with the logical tape(operation 1002) are illustrated in accordance with one approach. One ormore of such sub-operations may be used to perform operation 1002 ofFIG. 10A, however, such sub-operations are in no way intended to limitdescriptions herein.

Sub-operation 1004 includes writing a first identifier to an index ofthe logical tape. In one approach, the first identifier may representthe first physical tape and the first tape storage library as thelocation of the first physical tape. Sub-operation 1006 includes writinga second identifier to the index of the logical tape. In one approach,the first identifier may represent the second physical tape and thesecond tape storage library as the location of the second physical tape.Any type of conventional metadata may be used to create the identifiers.

It should be noted that in some approaches, a user may control, e.g.,assign, which physical tapes are to be associated with the logical tape.In one specific approach, a user's assignment of which tapes are to beassigned to the logical tape may be received prior to an exportoperation, e.g., where at least some distributed data of a storagesystem is migrated to a single physical tape.

Referring again to FIG. 10A, method 1000 includes storing the index ofthe logical tape in memory, e.g., see operation 1008. According tovarious approaches, the memory may include any type of memory. Forexample, in one approach, the type of memory in which the index of thelogical tape is stored may be different than the type of memory in whichthe logical tape is represented/stored.

In operation 1010, the logical tape is displayed by reading the indexfrom memory as a file system. In one approach, the file system may bedisplayed on an output interface for a user, where the logical tape ispresented to a user as a subfolder. For example, assuming that the mountpoint is /mnt/mtfs, /mnt/mtfs/USR001L7 is presented to users as thesubfolder, where USR001L7 is the logical tape identifier.

Various optional reading and/or writing operations that may be includedin method 1000 will now be described.

For example, in various approaches, method 1000 may include one or moreoperations for fulfilling a request to write data. In one of suchapproaches, in response to receiving the request to write data, method1000 includes identifying both the first physical tape and the secondphysical tape as a destination to which the data is to be written. Inanother of such approaches, in response to receiving the request to readdata, method 1000 includes identifying both the first physical tape andthe second physical tape as a destination from which the data is to beread.

Accordingly, in one approach, the data is written on both the firstphysical tape and the second physical tape. In preferred approaches, thedata written on both the first physical tape and the second physicaltape may be duplicates. As will be described elsewhere herein, as aresult of writing the data on both the first physical tape and thesecond physical tape, either of such tapes may be used for subsequentlyaccessing the data.

It should be noted that the data may be immediately written on both thefirst physical tape and the second physical tape, or a writing of thedata may be scheduled for a later time, e.g., after a current writingevent is completed.

The index of the logical tape may be updated to reflect informationabout the written data. For example, according to various approaches,the index of the logical tape may be updated to reflect typical indexinformation, e.g., a location of the data on the first physical tape, alocation of the data on the second physical tape, file size, etc.

As previously mentioned elsewhere herein, in one approach, in responseto any processing being performed, e.g., the writing of the data, thenaming of the file, etc., the index file of the logical tape may beupdated.

Moreover, in some approaches, managing the first storage library and thesecond storage library includes deleting data from the first physicaltape and/or the second physical tape that is accessed less than apredetermined amount, e.g., thereby considered stale/cold data.Accordingly, in one approach, a frequency of accesses to data isdetermined. The data may include any data that is stored on the firstphysical tape and/or the second physical tape.

A frequency of accesses to the data may be determined using any one ormore known methods, such as an auditing of an access history of thedata, accessing a count that is added to each time that the data isaccessed, receiving an indication of the frequency of accesses to thedata, etc.

In one approach, the determined frequency is compared to a predeterminedthreshold. The predetermined threshold may be dynamically adjusted atany time, e.g., in response to determining an overall performance in thefirst storage library and/or overall performance in the second storagelibrary decreases, in response to determining an overall performance inthe first storage library and/or overall performance in the secondstorage library increases, in response to determining that the storagecapacity of the first storage library and/or the second storage librarychanges, etc.

In response to determining that the determined frequency is less than orequal to the predetermined threshold, in one approach, an instructionmay be sent to reformat one of the identified physical tapes fordeleting the data from at least one of the reformatted physical tapes.According to various approaches, a reformatting of one of the identifiedphysical tapes may include, e.g., reformatting some or all of the tape,deleting a pointer to the data on one of the physical tapes from theindex of the logical tape, performing garbage collection, etc.

However, in another approach, in response to determining that thedetermined frequency is greater than the predetermined threshold, anoptional operation of method 1000 includes instructing the data to bewritten to a cache and/or to another physical tape of a library reservedfor data having a relatively high access frequency. For example, in oneapproach, in response to determining that the determined frequency isgreater than the predetermined threshold, method 1000 includesinstructing the data to be written to a third physical tape in a thirdstorage library. Moreover, in such an approach, the third physical tapemay be associated with the logical tape. For example, a third identifiermay be written to the index of the logical tape, e.g., where the thirdidentifier represents the third physical tape and the third storagelibrary. In one approach, the index of the logical tape is updated toreflect the written data.

Writing the data to one or more of such locations may enable a quickerread-back of the data than would otherwise be available in reading thedata from the physical tape having the data. Depending on the approach,in response to writing the data to such a location, a reformattinginstruction for for deleting the data from at least one of the physicaltapes may be sent. Deleting the data may free-up storage space on thereformatted physical tape, e.g., for subsequent data writing operations.

In another approach, the data may be left alone on the physical tapes inresponse to determining that the determined frequency is greater thanthe predetermined threshold.

In response to receiving a request for data that was previously writtenon one or both the first physical tape and the second physical tape, theindex of the logical tape is read for identifying the location of thedata. Using the index, the first physical tape and the second physicaltape are identified as storage on which the data is stored. Moreover,with the location of the data identified, one of the identified physicaltapes may be selected as a source tape from which the data is to beread.

Of course, a read request for other data may additionally and/oralternatively be received. For example, assume a request is received fordata that is not stored on the first physical tape and that is notstored on the second physical tape, but is stored on a third physicaltape and a fourth physical tape (that reside in the first storagelibrary and the second storage library respectively). In such anapproach, the index of the logical tape may be read, and locationidentifiers for the third and fourth physical tapes are found in theindex as being associated with the request data. Accordingly, thephysical tapes on which the data is stored are identified. In oneapproach, one of the identified physical tapes is selected as a sourcetape from which the data is to be read. The read request is sent to theserver and/or library associated with the selected physical tape withthe identification information of the data to be retrieved and physicaltape having the data thereon.

It should be noted that the processing of read operations of variousapproaches and/or embodiments described herein is configured to promptlyfulfill read requests for data as a result of data being duplicated on aplurality of physical tapes, thereby increasing accessibility to thedata. Accordingly, because the data may be stored on multiple physicaltapes, and one of the tapes is typically more readily accessible thanthe other, the physical tape estimated to provide fastest relativeread-back time may be selected to serve the read request.

Selection of one of multiple tapes having a copy of requested data asthe source tape may consider any one or more variables, as will now bedescribed below.

In one approach, selection of the source tape includes determining atime to perform a read-back of the data for each of the physical tapesidentified as having a copy of the data thereon. In such an approach,the physical tape having a shortest of the read-back times may beselected as the source tape.

In some other approaches, the selection of a source tape may includemaintaining and considering a priority scoring of the identifiedphysical tapes. For example, one approach includes assigning a priorityscore to each of the identified physical tapes based on an associateduse of each of the identified physical tapes. An illustrative approachfor such assigned scoring will now be described according to variousapproaches.

In one approach, a physical tape that is mounted on a drive and is notcurrently being used is assigned a higher priority score than a physicaltape that is not mounted on a drive and is not currently being used,e.g., for a read operation, for a write operation, being burnished, etc.Moreover, in one approach, a physical tape that is not mounted on adrive and is not currently being used for some process is assigned ahigher priority score than a physical tape that is mounted on a driveand is currently being used for some process. Furthermore, a physicaltape that is mounted on a drive and currently being used for someprocess may be assigned a higher priority score than a physical tapethat has been moved outside of a library.

Accordingly, in one approach, an assigned priority score may bedetermined for each of the identified physical tapes. The physical tapehaving a highest of the priority scores may be selected as the selectedsource tape.

In contrast, in other approaches, the priority scoring may alternativelyinclude assigning the above mentioned physical tapes an oppositeordering as that described above, e.g., “lower” priority score insteadof “higher” priority score. In such approaches, a physical tape having alowest of the priority score may be selected as the source tape.

In some approaches, read operations may include reading data from aplurality of different physical tapes concurrently. For example, a firstpart of the data may be read from the first physical tape, and aremaining part of the data may be read from the second physical tape. Inapproaches where this practice is applied to all data read events andall data write events, the effective storage capacity of the system maybe reduced to half of the total capacity that the system would otherwisehave if data was stored only a single time within the system. However,there are numerous benefits to implementing this scheme of splittingdata read operations across multiple physical source tapes. For example,such a scheme may offer improved reliability and accessibility of thedata. In contrast, because of duplicate instances of data, the trade-offis a reduction of overall storage capacity of the system, e.g., makingone duplicate per data file reduces a system's potential storagecapacity in half. Thus, an optimum number of duplicates may bedetermined according to the use case of the system.

For example, to improve the accessibility and the reliability of data,data is preferably stored in a plurality of tape cartridges to maintainredundancy of data. Further, libraries may be installed at remote sitesso as to prevent data loss in the event of disasters. Meanwhile, whenconsidering the capacity of the system that includes such libraries, thenumber of physical tapes storing duplicate data may be regulated inaccordance with the frequency of accesses to such physical tapes and/orthe data. For example, for data that has not been access in a certainperiod of time, one duplicate of the data may be deleted from one of thephysical tapes that include a copy of the data thereon, thereby freeingup capacity for other data. Accordingly, a balance between capacity andaccessibility is established.

It should be noted that in some approaches, one or more known algorithmsmay be used when selecting a physical tape for deletion of data. In oneapproach, such algorithm(s) are used in selecting a physical tape onwhich the data is to be deleted, so that as many files as possible areaggregated in one tape, or, on the contrary, files are distributed overas many different physical tapes as possible. It should also be notedthat due to the nature of physical tape storage being a sequential writemedium, management of the number of physical tapes that contain a copyof data may include an operation called “re-claim,” which copies onlyvalid data to other mediums, for the purposes of freeing up storagespace on a physical tape.

Scheme of Making an Association Between Logical Tape Cartridge andPhysical Tape Cartridge of MTFS

Various examples of associating the first physical tape and the secondphysical tape with the logical tape within a MTFS will now be describedin greater detail.

The MTFS may be implemented by making the modifications described belowto an LE based system. Accordingly, description is given of an exemplaryapproach in which a LE system is used as a lower layer LE system.However, the lower LE system may be modified to enable lower levelcommunication, such as per-block communication, between the MTFS and theLE system. Of course, the present descriptions are not intended to limitthe method for communication between the MTFS and the LE system.

An index file is extended so as to enable storing a plurality of sets ofassociated “library name(s)” and “physical tape name(s)”. For example, aformat such as that found in the portions of the index file 1100 of FIG.11 may be used for prefacing a portion of an LTFS index file inaccordance with IBM LTFS.

An “<extent>” portion of the index file is represented by replacing theportions of the index file with “<associated_tape>”, e.g., see portionsof index file 1200 of FIG. 12.

The “extended” index file is created per logical tape, and may be storedon, e.g., a server on which the MTFS is operating, a device such as acomputer on which method 1000 is being performed, a server that is beingmanaged, etc.

When access to a file is requested, the MTFS refers to those addedentries, and forwards the request to the corresponding lower LE system.

The request is made with a path name to the file, in which path name alogical tape cartridge name is inserted. The logical tape cartridge nameinserted in the path name is the name of the directory located under themount point of the lower LTFS and having that cartridge name.

Example 1

Making an association between logical tape and physical tape.

A command within a MTFS is created to enable assignment of a physicaltape to a logical tape. The MTFS accepts the command and writesinformation of the assigned physical tape and the library containing thephysical tape, into the index file of the MTFS. Of course, this exampleis not intended to limit any embodiments and/or approaches describedherein.

The MTFS may be configured to automatically select a tape one by onefrom each of the lower LE systems and make the assignment. Alternativelyand/or additionally, the MTFS may be configured to monitor tape capacityduring operation and add a physical tape to be assigned dynamically asneeded. Alternatively and/or additionally, MTFS may be configured toallow users to specify the size of the logical tape when making anassignment.

Example 2

Writing a file into a logical tape cartridge USR001L7

In the file system provided by the MTFS, a logical tape cartridge may bepresented as a subfolder. Assume in the present example that the mountpoint: /mnt/mtfs, /mnt/mtfs/USR001L7 is presented to users as thesubfolder.

A user issues a command for writing a file, e.g.,cp˜/myfile.dat/mnt/mtfs/USR001L7.

The MTFS receives the request to write, refers to the index file ofUSR001L7, and recognizes that USR001L7 is associated with PHY001L7 ofthe library 0000LB123456_L00.

The MTFS temporarily caches the file received from the user, and issuesa request for writing the cached file to the server that has activatedthe LE system using the library 0000LB123456_L00. In this processing,the MTFS inserts the logical tape cartridge name:

    scp ~/cachefile libraryserver:/mnt/ltfs/PHY001L7/USR001L7/myfile.dat

It should be noted that although a secure copy (scp) command is used forpurposes of an example, the scp command may, in some approaches, not beused, e.g., depending on the communication method between the MTFSsystem and the lower LE system.

Upon completion of processing, the MTFS updates its index file.

Example 3

Reading the file from the logical tape cartridge USR001L7.

In a file system provided by the MTFS, a logical tape cartridge ispresented to users as a subfolder. Thus, an access to the file may bemade under the directory /mnt/mtfs/USR001L7, e.g., using:cp/mnt/mtfs/USR001L7/myfile.dat˜

The MTFS receives the read request and identifies, on the basis of theindex file, a lower layer LE system which keeps the file. A request isissued for reading the file to the LE system. For example, a scp commandmay be used.

The MTFS sends the file read from the lower LE system to the user.

Using the implementation of the present example, a logical tapecartridge can be assigned to a plurality of physical tape cartridges.This is beneficial because one physical tape can keep data of aplurality of logical tapes. For example, it is possible to associatelogical tape (A) with physical tapes (a) and (b), and associate logicaltape (B) with physical tapes (b) and (c).

Additionally, physical tapes associated with one logical tape to bemanaged by different tape libraries.

Writing to a Plurality of Physical Tapes of MTFS

An example detailing writing to a plurality of physical tapes of MTFSwill now be described.

When the MTFS writes a file into a tape, such as in the above example,the MTFS may write into not only one physical tape cartridge but alsointo a plurality of physical tape cartridges in parallel.

When a file thereby recorded on the plurality of physical tapecartridges is read in the read processing of the example above, the MTFSmay select and use one physical tape cartridge from the plurality ofphysical tape cartridges that allows faster reading than other physicaltape cartridges, on the basis of the use situation of each of thosephysical tape cartridges.

Example

The physical tape cartridges associated with a logical tape cartridgeare each scored in accordance with the following rules:

-   -   The tape cartridge is mounted on a drive and is not currently        being used for a process: 5    -   The tape cartridge is not mounted on a drive and is not        currently being used for a process: 4    -   The tape cartridge is mounted on a drive and is currently being        used for a process: 3    -   The tape cartridge has been moved to the outside of the library:        0        Of course, the scores assigned in the present example are for        purposes of a non-limiting example only. Accordingly, any        scoring system may be applied to such cases.

The MTFS uses one of the physical tape cartridges that obtains thehighest score. Any of a plurality of physical tape cartridges whichobtain the same highest score may be used. Further, the MTFS may beconfigured to select a tape cartridge from which the data can be read ina shorter time period, by taking into account the position of the headrelative to the data on the tape, or the like in the tape cartridge.

Further, the same file may be read from the plurality of tapes at thesame time. In this case, a former part of the file and a latter part ofthe file may be separately read and combined to form the complete file.

Where duplication is applied to all the files in a data storage system,the effective storage capacity of the whole system will be reduced inhalf. However, it is advantageous if a larger number of duplicates arestored in the system, in view of the improvement in the reliability andaccessibility of the data. Accordingly, in some approaches, a number ofduplicates and/or which data to duplicate may be determined according tothe use case of the system.

When emphasizing the accessibility and the reliability of data, data ispreferably stored in a plurality of tape cartridges as duplicates tomaintain redundancy of data. Furthermore, data may be duplicated acrosslibraries installed at remote sites so as to prevent data loss in theevent of disasters.

Meanwhile, when emphasizing the capacity, the number of physical tapecartridges on which duplicates of data are stored, and/or the amount ofdata that is duplicated, may be controlled according to some criteriasuch as the frequency of accesses to the data. For example, for a fileto which no access is made in a certain period of time, one duplicate ofthe file may be deleted from one of the plurality of physical tapes. Byimplementing this feature, a balance between capacity and accessibilitycan be established.

One or more algorithms may be used when selecting a physical tape fromwhich the data is deleted. For example, the physical tape from which thedata is deleted may be selected so that as many files as possible areaggregated in one tape, or, on the contrary, files are distributed overas many different tapes as possible. It should be noted, that due to thenature of tape storage being a sequential write medium, such processingmay include an operation called “reclaim,” which copies only valid datato other medium(s), for purposes of reusing tape cartridges. Whendynamically controlling the number of duplicates in the variousembodiments and/or approaches herein, reclaim operations may beregularly performed.

The benefits of various embodiments and/or approaches described hereinshould further be considered in view of conventional Redundant Array ofIndependent Disks (RAID) techniques. For example, conventional RAIDtechniques often utilize a plurality of sets of physical tapes, and as aresult may have issues with maintaining the combinations of sets ofphysical tapes. In contrast, various embodiments and/or approachesdescribed herein enable reading a file, e.g., instance of data, usingonly a single physical tape in some approaches, without having tomaintain specific combinations of physical tapes.

Additionally, various embodiments and/or approaches described hereinshould not be interpreted as simply making duplicates of data. Rather,the various embodiments and/or approaches described herein enableeffective utilization of a storage capacity of a system, by reducing thenumber of duplicates of instances of data that have a relatively lowaccess frequency. Meanwhile, data having a relatively high accessfrequency are awarded, e.g., duplicity, a higher priority, placement ina cache, placement on a physical tape of a storage library reserved forfrequently used data, etc. Accordingly, based on use of data in aplurality of storage libraries, data characterized as having arelatively high access frequency and/or priority may be, e.g., migratedto quickly accessible portions of a storage system, duplicated, notdeleted from physical tape, etc.

File Duplication by MTFS

An example detailing file duplication by MTFS will now be described.

Elsewhere above, the descriptions of writing data to a plurality ofphysical tapes describe securing capacity within a storage system byreducing the number of duplicates of files having a low accessfrequency. Meanwhile, files with a particularly high access frequencymay be duplicated in separate tapes in separate libraries.

In one example, for a file with a predetermined number of accesses in apredetermined period of time, the frequency of the accesses to the filemay be counted and recorded. After the predetermined period of timepasses, in response to determining that a file has an access frequencygreater than a predetermined threshold value, the MTFS creates aduplicate in a physical tape cartridge selected from the physical tapecartridges corresponding to the logical tape cartridge (provided thatthe physical tape of the selected cartridge does not already contain aduplicate of the file). The MTFS creates the duplicate by making a copyof the file through the MTFS.

In order to duplicate data, a MTFS may instruct a lower layer LE systemto create a duplicate of data in a separate physical tape and move thephysical tape to a different storage library with a relatively fasteraccess time. Of course, the methods for making duplicates of data arenot limited thereto, e.g., see other approaches and/or embodimentsdescribed elsewhere herein.

Moreover, various approaches and/or embodiments described herein do notsimply maintain files redundantly. Instead, various approaches and/orembodiments described herein enable distribution of data across physicaltapes. From this, a reduction of network load associated withduplication will result. Accordingly, various ones of the approachesand/or embodiments described herein may prove particular useful formoving a large number of data files each having a large data size fromone storage library to a different storage library.

FIG. 13 depicts a data storage system 1300, in accordance with oneembodiment. As an option, the present data storage system 1300 may beimplemented in conjunction with features from any other embodimentlisted herein, such as those described with reference to the other FIGS.Of course, however, such data storage system 1300 and others presentedherein may be used in various applications and/or in permutations whichmay or may not be specifically described in the illustrative embodimentslisted herein. Further, the data storage system 1300 presented hereinmay be used in any desired environment.

Data storage system 1300 includes a first physical tape 1306 of a firststorage library 1302 and a second physical tape 1308 of a second storagelibrary 1304. Similar to operation 1002 of method 1000, the firstphysical tape 1306 and the second physical tape 1308 may be associatedwith a logical tape. Note that in FIG. 13, software of serverM 1312 isrunning MTFS. Accordingly, the logical tape is displayed to a userapplication 1314 as residing on the serverM 1312.

The association includes writing a first location identifier, e.g.,/mtfs/<vTapeIDv>/mydir/myfile.txt, to an index 1310 of the logical tapevTapeIDv. The first location identifier represents the first physicaltape 1306 and the first storage library 1302. Moreover, the associationincludes writing a second location identifier, e.g.,/mtfs/<vTapeIDv>/yrdir/yrfile.txt, to the index 1310 of the logical tapevTapeIDv. The second location identifier represents the second physicaltape 1308 and the second storage library 1304.

The index 1310 of the logical tape vTapeIDv is stored in memory, e.g.,of the MTFS.

Moreover, the logical tape vTapeIDv is displayed by reading the index1310 from memory as a file system. For example, note that the userapplication 1314 can access physical tapes 1306, 1308 of either of thestorage libraries 1302, 1304 via the logical tape vTapeIDv, withouthaving to know in which storage library the requested data resides. Thisis because the index 1310 of the logical tape vTapeIDv accounts for suchinformation. Accordingly, despite data storage system 1300 including aplurality of servers, e.g., ServerA and ServerB, associated with thestorage libraries 1302, 1304, the access path of each of the serversfrom the user application 1314 is identical, e.g., see access path 1316.

It should be noted that in various other approaches, the data storagesystem 1300 may include servers in addition to ServerA and ServerB andtape libraries in addition to the storage libraries 1302, 1304, e.g., athird library, a third server, a fourth library, a fourth server, and soon, in any combination, for purposes of scaling out the data storagesystem 1300 when doing so would benefit the data storage system 1300.

The configuration of the data storage system 1300 allows a logical tapecartridge to be assigned to a plurality of physical tape cartridges.Moreover, the configuration of the data storage system 1300 is unique inthat one physical tape can store data of a plurality of logical tapes.For example, it is possible to associate a first logical tape, e.g.,vTapeIDv, with physical tapes 1306, 1308, and associate a differentlogical tape (not shown) with physical tapes 1308, 1318.

Additionally, the configuration of the data storage system 1300 allowsphysical tapes associated with one logical tape to be managed bydifferent tape libraries.

These configurations and various embodiments and/or approaches describedherein provide a logical tape for a user and internally associates aplurality of physical tapes with the logical tape. Availability ofaccess to a file of data also improves as a result of recordingduplicates of the file into a plurality of tape cartridges upon arequest to write the data.

It should be noted however, that the number of copies of the data willnot become excessive (which would otherwise waste storage space in thesystem), because the number of the copies/duplicates of the data iscontrolled on a basis of, e.g., frequency access to the data, priorityscores, etc. Moreover, data with the highest access frequently and/orpriority may be placed in a higher storage tier, e.g., such as in acache.

The present invention may be a system, a method, and/or a computerprogram product. The computer program product may include a computerreadable storage medium (or media) having computer readable programinstructions thereon for causing a processor to carry out aspects of thepresent invention.

The computer readable storage medium can be a tangible device that canretain and store instructions for use by an instruction executiondevice. The computer readable storage medium may be, for example, but isnot limited to, an electronic storage device, a magnetic storage device,an optical storage device, an electromagnetic storage device, asemiconductor storage device, or any suitable combination of theforegoing. A non-exhaustive list of more specific examples of thecomputer readable storage medium includes the following: a portablecomputer diskette, a hard disk, a random access memory (RAM), aread-only memory (ROM), an erasable programmable read-only memory (EPROMor Flash memory), a static random access memory (SRAM), a portablecompact disc read-only memory (CD-ROM), a digital versatile disk (DVD),a memory stick, a floppy disk, a mechanically encoded device such aspunch-cards or raised structures in a groove having instructionsrecorded thereon, and any suitable combination of the foregoing. Acomputer readable storage medium, as used herein, is not to be construedas being transitory signals per se, such as radio waves or other freelypropagating electromagnetic waves, electromagnetic waves propagatingthrough a waveguide or other transmission media (e.g., light pulsespassing through a fiber-optic cable), or electrical signals transmittedthrough a wire.

Computer readable program instructions described herein can bedownloaded to respective computing/processing devices from a computerreadable storage medium or to an external computer or external storagedevice via a network, for example, the Internet, a local area network, awide area network and/or a wireless network. The network may comprisecopper transmission cables, optical transmission fibers, wirelesstransmission, routers, firewalls, switches, gateway computers and/oredge servers. A network adapter card or network interface in eachcomputing/processing device receives computer readable programinstructions from the network and forwards the computer readable programinstructions for storage in a computer readable storage medium withinthe respective computing/processing device.

Computer readable program instructions for carrying out operations ofthe present invention may be assembler instructions,instruction-set-architecture (ISA) instructions, machine instructions,machine dependent instructions, microcode, firmware instructions,state-setting data, or either source code or object code written in anycombination of one or more programming languages, including an objectoriented programming language such as Smalltalk, C++ or the like, andconventional procedural programming languages, such as the “C”programming language or similar programming languages. The computerreadable program instructions may execute entirely on the user'scomputer, partly on the user's computer, as a stand-alone softwarepackage, partly on the user's computer and partly on a remote computeror entirely on the remote computer or server. In the latter scenario,the remote computer may be connected to the user's computer through anytype of network, including a local area network (LAN) or a wide areanetwork (WAN), or the connection may be made to an external computer(for example, through the Internet using an Internet Service Provider).In some embodiments, electronic circuitry including, for example,programmable logic circuitry, field-programmable gate arrays (FPGA), orprogrammable logic arrays (PLA) may execute the computer readableprogram instructions by utilizing state information of the computerreadable program instructions to personalize the electronic circuitry,in order to perform aspects of the present invention.

Aspects of the present invention are described herein with reference toflowchart illustrations and/or block diagrams of methods, apparatus(systems), and computer program products according to embodiments of theinvention. It will be understood that each block of the flowchartillustrations and/or block diagrams, and combinations of blocks in theflowchart illustrations and/or block diagrams, can be implemented bycomputer readable program instructions.

These computer readable program instructions may be provided to aprocessor of a general purpose computer, special purpose computer, orother programmable data processing apparatus to produce a machine, suchthat the instructions, which execute via the processor of the computeror other programmable data processing apparatus, create means forimplementing the functions/acts specified in the flowchart and/or blockdiagram block or blocks. These computer readable program instructionsmay also be stored in a computer readable storage medium that can directa computer, a programmable data processing apparatus, and/or otherdevices to function in a particular manner, such that the computerreadable storage medium having instructions stored therein comprises anarticle of manufacture including instructions which implement aspects ofthe function/act specified in the flowchart and/or block diagram blockor blocks.

The computer readable program instructions may also be loaded onto acomputer, other programmable data processing apparatus, or other deviceto cause a series of operational steps to be performed on the computer,other programmable apparatus or other device to produce a computerimplemented process, such that the instructions which execute on thecomputer, other programmable apparatus, or other device implement thefunctions/acts specified in the flowchart and/or block diagram block orblocks.

The flowchart and block diagrams in the Figures illustrate thearchitecture, functionality, and operation of possible implementationsof systems, methods, and computer program products according to variousembodiments of the present invention. In this regard, each block in theflowchart or block diagrams may represent a module, segment, or portionof instructions, which comprises one or more executable instructions forimplementing the specified logical function(s). In some alternativeimplementations, the functions noted in the block may occur out of theorder noted in the figures. For example, two blocks shown in successionmay, in fact, be executed substantially concurrently, or the blocks maysometimes be executed in the reverse order, depending upon thefunctionality involved. It will also be noted that each block of theblock diagrams and/or flowchart illustration, and combinations of blocksin the block diagrams and/or flowchart illustration, can be implementedby special purpose hardware-based systems that perform the specifiedfunctions or acts or carry out combinations of special purpose hardwareand computer instructions.

Moreover, a system according to various embodiments may include aprocessor and logic integrated with and/or executable by the processor,the logic being configured to perform one or more of the process stepsrecited herein. By integrated with, what is meant is that the processorhas logic embedded therewith as hardware logic, such as an applicationspecific integrated circuit (ASIC), a field programmable gate array(FPGA), etc. By executable by the processor, what is meant is that thelogic is hardware logic; software logic such as firmware, part of anoperating system, part of an application program; etc., or somecombination of hardware and software logic that is accessible by theprocessor and configured to cause the processor to perform somefunctionality upon execution by the processor. Software logic may bestored on local and/or remote memory of any memory type, as known in theart. Any processor known in the art may be used, such as a softwareprocessor module and/or a hardware processor such as an ASIC, a FPGA, acentral processing unit (CPU), an integrated circuit (IC), a graphicsprocessing unit (GPU), etc.

A data processing system suitable for storing and/or executing programcode may include at least one processor, which may be or be part of acontroller, coupled directly or indirectly to memory elements through asystem bus, such as processor 400 of FIG. 4. The memory elements caninclude local memory employed during actual execution of the programcode, such as nonvolatile memory 404 of FIG. 4, bulk storage, and cachememories which provide temporary storage of at least some program codein order to reduce the number of times code must be retrieved from bulkstorage during execution.

It will be clear that the various features of the foregoing systemsand/or methodologies may be combined in any way, creating a plurality ofcombinations from the descriptions presented above.

It will be further appreciated that embodiments of the present inventionmay be provided in the form of a service deployed on behalf of acustomer to offer service on demand.

While various embodiments have been described above, it should beunderstood that they have been presented by way of example only, and notlimitation. Thus, the breadth and scope of an embodiment of the presentinvention should not be limited by any of the above-described exemplaryembodiments, but should be defined only in accordance with the followingclaims and their equivalents.

What is claimed is:
 1. A computer-implemented method for managing afirst storage library and a second storage library, thecomputer-implemented method comprising: associating a first physicaltape and a second physical tape with a logical tape, wherein theassociating includes: writing a first identifier to an index of thelogical tape, wherein the first identifier represents the first physicaltape and the first storage library, and writing a second identifier tothe index of the logical tape, wherein the second identifier representsthe second physical tape and the second storage library; storing theindex of the logical tape in memory; displaying the logical tape byreading the index from memory as a file system; receiving a read requestfor data; reading the index of the logical tape; identifying on which ofthe physical tapes the requested data is stored; assigning a priorityscore to each of the identified physical tapes based on an associateduse of each of the identified physical tapes, wherein the priorityscores are assigned such that: a physical tape that is mounted on adrive and is not currently being used is assigned a higher priorityscore than a physical tape that is not mounted in a drive and is notcurrently being used; a physical tape that is not mounted in a drive andis not currently being used is assigned a higher priority score than aphysical tape that is mounted in a drive and is currently being used;and a physical tape that is mounted in a drive and is currently beingused is assigned a higher priority score than a physical tape that hasbeen moved outside of a library; determining an assigned priority scorefor each of the identified physical tapes; and selecting the physicaltape having a highest of the priority scores as a source tape from whichthe requested data is to be read.
 2. A computer-implemented method asrecited in claim 1, comprising: in response to receiving a request towrite data: identifying both the first physical tape and the secondphysical tape as a destination to which the data associated with thewrite request is to be written, wherein the first storage library is alocation of the first physical tape, wherein the second storage libraryis a location of the second physical tape; writing the data associatedwith the write request to both the first physical tape and the secondphysical tape; and updating the index of the logical tape to reflect thewritten data.
 3. A computer-implemented method as recited in claim 2,comprising: receiving a read request for the written data; reading theindex of the logical tape; identifying the first physical tape and thesecond physical tape as storage on which the written data is stored; andselecting one of the first physical tape and the second physical tape asa source tape from which the written data is to be read.
 4. Acomputer-implemented method as recited in claim 1, comprising:determining a frequency of accesses to the requested data; comparing thedetermined frequency with a predetermined threshold; and in response todetermining that the determined frequency is less than or equal to thepredetermined threshold, deleting the requested data from at least oneof the physical tapes.
 5. A computer-implemented method as recited inclaim 3, wherein selecting one of the first physical tape and the secondphysical tape as the source tape from which the written data is to beread includes: determining, for each of the first physical tape and thesecond physical tape, a time to perform a read-back of the written data;and selecting the physical tape having a shortest of the read-back timesas the selected source tape from which the written data is to be read.6. A computer-implemented method as recited in claim 1, comprising:determining a frequency of accesses to data stored on both the first andsecond physical tapes; comparing the determined frequency with apredetermined threshold; and in response to determining that thedetermined frequency is less than or equal to the predeterminedthreshold, deleting the data stored on both the first and secondphysical tapes from at least one of the physical tapes.
 7. Acomputer-implemented method as recited in claim 6, comprising: inresponse to determining that the determined frequency is greater thanthe predetermined threshold, instructing the data stored on both thefirst and second physical tapes to be written to a cache.
 8. Acomputer-implemented method as recited in claim 6, comprising: inresponse to determining that the determined frequency is greater thanthe predetermined threshold, instructing the data stored on both thefirst and second physical tapes to be written to a third physical tapein a third storage library; associating the third physical tape with thelogical tape, wherein the associating includes: writing a thirdidentifier to the index of the logical tape, wherein the thirdidentifier represents the third physical tape and the third storagelibrary; and updating the index of the logical tape to reflect thewritten data.
 9. A computer program product for managing a first storagelibrary and a second storage library, the computer program productcomprising a computer readable storage medium having programinstructions embodied therewith, wherein the computer readable storagemedium is not a transitory signal per se, the program instructionsreadable and/or executable by a controller to cause the controller toperform a method comprising: associating, by the controller, a firstphysical tape and a second physical tape with a logical tape, whereinthe associating includes: writing a first identifier to an index of thelogical tape, wherein the first identifier represents the first physicaltape and the first storage library as a location of the first physicaltape, and writing a second identifier to the index of the logical tape,wherein the second identifier represents the second physical tape andthe second storage library as a location of the second physical tape;storing, by the controller, the index of the logical tape in memory;displaying, by the controller, the logical tape by reading the indexfrom memory as a file system; in response to receiving a request towrite data: identifying, by the controller, both the first physical tapeand the second physical tape as a destination to which the data is to bewritten; writing, by the controller, the data to both the first physicaltape and the second physical tape; and updating, by the controller, theindex of the logical tape to reflect the written data, wherein the indexof the logical tape is stored in a different type of memory than amemory in which the logical tape is stored.
 10. A computer programproduct as recited in claim 9, the program instructions readable and/orexecutable by the controller to cause the controller to perform themethod comprising: receiving, by the controller, a read request for thewritten data; reading, by the controller, the index of the logical tape;identifying, by the controller, the first physical tape and the secondphysical tape as storage on which the written data is stored; andselecting, by the controller, one of the identified physical tapes as asource tape from which the written data is to be read.
 11. A computerprogram product as recited in claim 9, the program instructions readableand/or executable by the controller to cause the controller to performthe method comprising: determining, by the controller, a frequency ofaccesses to the written data; comparing, by the controller, thedetermined frequency with a predetermined threshold; and in response todetermining that the determined frequency is less than or equal to thepredetermined threshold, deleting, by the controller, the written datafrom at least one of the physical tapes.
 12. A computer program productas recited in claim 9, the program instructions readable and/orexecutable by the controller to cause the controller to perform themethod comprising: receiving, by the controller, a read request fordata; reading, by the controller, the index of the logical tape;identifying, by the controller, on which of the physical tapes therequested data is stored; and selecting, by the controller, one of thefirst physical tape and the second physical tape as a source tape fromwhich the requested data is to be read.
 13. A computer program productas recited in claim 12, wherein selecting the source tape from which therequested data is to be read includes: determining, by the controllerfor each of the physical tapes identified as having the requested datastored thereon, a time to perform a read-back of the requested data; andselecting, by the controller, the physical tape having a shortest of theread-back times as the selected source tape.
 14. A computer programproduct as recited in claim 12, wherein selecting the source tape fromwhich the requested data is to be read includes: assigning, by thecontroller, a priority score to each of the physical tapes identified ashaving the requested data stored thereon, wherein the assigning ofpriority scores is based on an associated use of each of the physicaltapes identified as having the requested data stored thereon, whereinthe priority scores are assigned such that: a physical tape that ismounted on a drive and is not currently being used is assigned a higherpriority score than a physical tape that is not mounted in a drive andis not currently being used; a physical tape that is not mounted in adrive and is not currently being used is assigned a higher priorityscore than a physical tape that is mounted in a drive and is currentlybeing used; and a physical tape that is mounted in a drive and iscurrently being used is assigned a higher priority score than a physicaltape that has been moved outside of a library; determining, by thecontroller, an assigned priority score for each of the physical tapesidentified as having the requested data stored thereon; and selecting,by the controller, the physical tape having a highest of the priorityscores as the selected source tape from which the requested data is tobe read.
 15. A computer program product as recited in claim 9, theprogram instructions readable and/or executable by the controller tocause the controller to perform the method comprising: determining, bythe controller, a frequency of accesses to data stored on both the firstand second physical tapes; comparing, by the controller, the determinedfrequency with a predetermined threshold; and in response to determiningthat the determined frequency is less than or equal to the predeterminedthreshold deleting, by the controller, the data stored on both the firstand second physical tapes from at least one of the physical tapes.
 16. Acomputer program product as recited in claim 15, the programinstructions readable and/or executable by the controller to cause thecontroller to perform the method comprising: in response to determiningthat the determined frequency is greater than the predeterminedthreshold, instructing, by the controller, the data stored on both thefirst and second physical tapes to be written to a third physical tapein a third storage library; associating, by the controller, the thirdphysical tape with the logical tape, wherein the associating includes:writing a third identifier to the index of the logical tape, wherein thethird identifier represents the third physical tape and the thirdstorage library; and updating, by the controller, the index of thelogical tape to reflect the data written to the third physical tape. 17.An apparatus, comprising: a processor; and logic configured to cause theprocessor of the apparatus to: associate, by the processor, a firstphysical tape of a first storage library and a second physical tape of asecond storage library with a logical tape, wherein the associatingincludes: writing a first identifier to an index of the logical tape,wherein the first identifier represents the first physical tape and thefirst storage library, and writing a second identifier to the index ofthe logical tape, wherein the second identifier represents the secondphysical tape and the second storage library; store, by the processor,the index of the logical tape in memory; receive, by the processor, aread request for data; read, by the processor, the index of the logicaltape; identify, by the processor, on which of the physical tapes thedata is stored; and select, by the processor, one of the identifiedphysical tapes as a source tape from which the data is to be read,wherein the selection is based on a previously assigned priority scoreof the selected physical tape, wherein the previously assigned priorityscore of the selected physical tape is based on an associated use ofeach of the identified physical tapes.